The invention relates to a device for measuring the mobility of the back or trunk of a patient by determining the travel of the three-dimensional absolute positions of at least three reference points in a reference area of the device relative to a stationary measuring device with a contact area forming a support plane.
It is known that the mobility of the trunk and/or back of a patient can be determined by gluing marking points on the back as reference points ("Study of Gait and Functional Spinal Column Measurement by Means of a Newly-Developed Real-Time Stereo Ultrasound Topometer (ESUT)," in Functional Diagnosis in Orthopedics, Enkeverlag, Stuttgart, 1979). Determination of the mobility of the back and trunk can provide valuable information.
In order to determine the absolute position of all the degrees of freedom of a specific part of the trunk, at least three differential points must be located per area of the trunk. The reference points can consist for example of ultrasonic transmitters or receivers whose position can be determined by a stationary measuring station, stationary measuring microphones or sonic transmitters for example, through measurements of running time (EP-0 305 780).
Other methods include the location of reflecting or light-emitting reference points by means of correspondingly stationary recording cameras with evaluation connected to them as a stationary measuring device.
In these known devices, it is disadvantageous that in severe forward tilting of the subject, the stationary measuring device can no longer be located, or can no longer be located accurately, because the body then comes between the area between the reference points and the stationary measuring device.